During the past year a method has been developed for measuring lymphocyte transformation to tuberculin using cells from mice that had been immunized with BCG. It is intended to apply these results to mice that have been infected with BCG in the lungs and use mediastinal lymph node spleen cells for the assay. It is also proposed to perform migration-inhibition tests in a similar way. Finally, similar experiments will be performed using lymphoid cells that have been freed from the lungs. This may present problems because of the small number of cells that are released.